1. Field of the Invention
This invention relates to electrical switches and more particularly to hermetically sealed switches with magnetic coupling between switch contacts and control levers.
2. Description of the Prior Art
Sealed, explosion proof switches are commonly used in special environments such as an explosive atmosphere wherein it is desirable to completely isolate switch contacts. This isolation protects the environment from any sparks that may be generated during switching and also protects the switching mechanism from the environment. In one arrangement of a sealed magnetic switch an outer follower magnet which makes electrical contacts is disposed in a chamber concentrically about a central, similarly poled control magnet. Selective axial positioning of the control magnet, in combination with repulsive forces of the control magnet and concentric follower magnet causes the follower magnet to move axially between first and second limits in accordance with the repulsive forces of the control magnet. In another arrangement, control and follower magnets are disposed side by side in similar mating pole relationship with repulsive forces therebetween inducing axial motion in the follower magnet in response to motion of the control magnet along a parallel axis to maintain the control and follower magnets at opposite limits of restricted travel paths. In other arrangements, moving seals between control and follower magnets defeat the goal of complete isolation. Such prior art arrangements are unable to provide the economy and flexibility of sealed switches in accordance with the invention while maintaining complete isolation of the electrical switching contacts.